Unable to key in valid phone number in Ming Dao Private Deployment

Hi, I'm trying to key in the following phone number +65-63857486 which is a valid singapore phone number. But I'm unable to key it into the telephone no data box because it is mentioned as not valid. I have tried the same number on a free mingdao.com account, this number is accepted as a valid number. Is there any way we can edit the phone number rule to make this a valid phone number? Thank you.